Pregnancy Due Date API

Pregnancy and due-date maths as an API, using the standard Naegele's rule (40 weeks / 280 days from the last menstrual period). The due-date endpoint takes the last menstrual period, the conception date, or a known due date — whichever you have — and returns the due date, the estimated conception date and the fertile window. The gestational-age endpoint reports how far along a pregnancy is as of any reference date: gestational age in weeks and days, the trimester, days remaining, progress percent, and whether it is overdue. The milestones endpoint lists the key dates of a pregnancy — the trimester boundaries, the anatomy-scan window, viability at 24 weeks, full term at 37–40 weeks, the due date and post-term at 42 weeks. All dates are handled in UTC and computed locally and deterministically. Ideal for pregnancy and fertility apps, midwifery and clinical tools, and parenting and family-planning products. Informational only — not medical advice. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 4 endpoints. This is pregnancy date maths; for general date arithmetic use a datetime API.